Whenever I call this function, it returns nil after one mouse click, idk why?

All I want it to do is to return a part with the given name.

script.FindMousePart.OnInvoke = function(NameOfPart)
	print('test')
	local finalpart
	local mouse = player:GetMouse()
	local function MouseThing()
		mouse.Button1Down:Wait(function()
		
		local part = mouse.target
		print('test2')
		if part.Name == NameOfPart then
			finalpart = part
			
			end
		end)
	end
	if finalpart ~= nil then
		return finalpart
	else
		MouseThing()
	end

end